As to a fuel cell system mounted in a vehicle or the like, various hybrid type fuel cell systems each comprising a fuel cell and a battery as power sources have been suggested to cope with a rapid variance of a load in excess of the power generation ability of a fuel cell (see, e.g., Patent Document 1 as follows).
FIG. 7 is a diagram illustrating a hybrid type fuel cell system (hereinafter referred to as the FCHV system) mounted in the vehicle. In an FCHV system 100, a fuel cell 110 and a battery 120 are connected in parallel with a load 130, and the load 130 is connected to an inverter 140 which converts a direct-current power supplied from the fuel cell 110 or the battery 120 into an alternate-current power. Moreover, between the fuel cell 110 and the inverter 140, a DC/DC converter (hereinafter referred to as the FC converter) 155 is provided which controls a terminal voltage (the output voltage) Vfc of the fuel cell 110, and between the battery 120 and the inverter 140, a DC/DC converter (hereinafter referred to as the battery converter) 150 is provided which controls an input voltage Vin of the inverter 140.
A controller 160 calculates a demand power for the load 130 based on a detection signal (e.g., a detection signal indicating the open degree of an accelerator pedal) supplied from a sensor group 170 including a sensor for the accelerator pedal and the like, and the controller controls the inverter 140 based on the calculated demand power, whereby a power corresponding to the demand power is supplied to the load 130 through the inverter 140.